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Planetary Detection Methods |
| Direct Detection This method entails actually imaging a planet directly as it orbits its parent star. Because of the huge technical problems yet to be overcome, however, this remains an unrealized dream. The most likely instrument, however, would be one which could image a planet in the infrared. Planets are kept warm in many ways, such as the heat of its gravitational contraction or the decay of radioactive elements within it. |
| Direct Spectroscopic Detection By imaging the spectrum of a star a number of times, it is possible to differentiate the spectrum of light being reflected off of planetary bodies. This is a relatively new technique, and is still being tested. |
| Astrometry The gravity of a planet orbiting a star, even one as small as the Earth, tugs on its sun, creating a wobble in the apparent motion of that star. Of course, smaller worlds have smaller wobble effects, and so greater refining techniques are needed to detect these planets. And the further a planet is from its star, the greater the amount of time is required to measure that wobble. the method is limited in that it requires the system to be viewed almost face on, as if we were looking at it from its "north or south pole". |
| Planetary Transits This measures the decrease in starlight as a planet orbits and passes in front of its star. the drawback is, of course, we must be viewing the star system nearly or completely edge on. |
| Doppler Technique Similar to the astrometry technique. But this method relies on viewing the star edge-on, and detecting the gravitational wobble as a shift in the spectrum. As the star wobbles away from us, the light shifts to the red. As it wobbles towards us, the light turns blue. |
| Pulsar Timing Technique As a pulsar rotates, it sends out a sweeping stream of energy. So precise is this rotation that the period can be timed down to the millisecond. The gravitational tug of any orbiting planet will cause this timing to be off by a certain amount, which can be translated into the orbital parameters of a planet and its mass. Because of how precise this can be timed, this method is capable of detecting Earth-massed objects. of course, in such a system, habitable worlds are almost certainly an impossibility. |
| Microlensing Technique When the light of a distant object, such as a star, galaxy, or quasar, passes directly behind a much nearer object with substantial mass, that light can be gravitationally deformed into a ring or arc. For instance, if the light from a galaxy passes directly behind that of a nearer star, from our point of view, it will arc. Now, if that nearby star has a planet in orbit of it, their position will make that arc of light suddenly brighten, and then dim, as the planet orbits. |
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© John M. and Margo
L. Dollan 2003 Other usages cited at Usage Permission Page This Page first uploaded November 21, 2003 Most recent update for this page November 21, 2003 Initial visual inspiration from M. Alan Kazlev's Paleos Website |